how to change number of segments
In 2.80 the panel to adjust the last operator has been moved out of the toolbar region into a floating panel at the bottom left of the viewport. This can be expanded/collapsed by clicking the top of the panel.



There is an option to hide this panel, it can be found in the 3D viewports View menu.



Even if the last operator panel is hidden, we can still bring it up manually with F9 - note that in 2.79 we use F6